Apparently its a "modified" VirusBuster engine, because it seems the update version numbers and pattern numbering differ from VirusBuster. However, from the look of it, there is very little, if any at all, detection rate difference between VirusBuster and PC Tools AV.

VirusBuster does, however, pass VB100, so I wouldn't call it "useless" per se, as such Spyware Doctor + Anti-Virus did not reach the minimum rating required for continuous rating for testing at AV-comparatives in the last single product test....